Method for synthesizing chain carbonate from metal ionic liquid

Abstract

The invention discloses a method for synthesizing chain carbonic ester from alkali metal ionic liquid. The chain carbonic ester comprises chain carbonic ester products of dimethyl carbonate and diethyl carbonate. The catalyst is characterized in that structural units of alkylamine cations, 1-methylimidazole cations, 1-butyl-3-methylimidazole cations, 1-butyl-2, 3-dimethylimidazole cations and pyridyl cations are respectively subjected to transesterification reaction with alkali metal ionic liquid formed by alkali metal halides including any one of ZnCl2, ZnBr2, FeCl3 and AlCl3, and the catalyst shown in the figure 1 is shown in the description, and the structural units of the alkylamine cations, the 1-methylimidazole cations, the 1-butyl-3-methylimidazole cations, the 1-butyl-2, 3-dimethylimidazole cations and the pyridyl cations are shown in the description. And when the using amount of the catalyst is 0.5-20wt%, the temperature is 50-120 DEG C, and the molar ratio of alcohol to ester is (1: 1)-(12: 1), the selectivity of the generated chain-like diester carbonate product is as high as 99.8%. The system can solve the problems of aggregation of a traditional alkyl alcohol catalyst and poor compatibility with cyclic ester, is beneficial to improvement of reaction selectivity, and avoids the phenomenon that the operation, separation and purification cost is increased due to hardening of the traditional catalyst.

Description

Technical Field

[0001] The invention belongs to the technical field of ion liquid catalytic synthesis of chain carbonates, and relates to a catalytic synthesis method for obtaining chain carbonates by ester exchange of cyclic carbonates. Background Art

[0002] The object of the present invention is to propose a system and method, which can make the system have high safety, stability and reliability. Carbonate is a green and environmentally friendly solvent with advantages such as low toxicity, low viscosity, high surface tension and low dielectric constant. Because its structure contains special functional groups such as alkoxy, carbonyl, alkyl and carbonyl alkoxy, it can be used as environmentally friendly chemical raw materials, replace phosgene as green carbonylation reagent or replace dimethyl sulfate as methylation reagent. It has been used to synthesize polycarbonate, isocyanate, polyurethane, polycarbonate diol and other chemical products. Its consumer market covers plastics, pesticides, medicine and electronics. Since 2017, my country's demand for dimethyl carbonate market has reached 2.673 billion yuan. By the end of 2022, the industry scale has increased significantly to 5.126 billion yuan. It is estimated that the growth rate during 2022-2028 will reach 22.0%, and it is expected to reach 36.4 billion yuan in 2028, and China will occupy about 80% of the global market share. However, with the development of the industry and the continuous improvement of the green industrial chain, the requirements for the quality of carbonate products, greening, safety and low energy consumption of synthesis routes and processes will become higher and higher in the future.

[0003] Adopt green, environmentally friendly and safe industrial technology routes, especially the ester exchange method, to prepare high-end chain carbonate products of battery grade or even electronic grade quality, develop high-tech industries of low-carbon symmetrical chain carbonates, and completely replace the carbonylation method and urea alcoholysis method with high energy consumption and high by-products. Using cyclic carbonates as raw materials, chain carbonates and diols are prepared by ester exchange reaction. Alkali metal salts, alkali metal oxides or alkali metal hydroxides are generally used as catalysts. Although the product yield is high, due to the limited solubility of inorganic alkali metals, it is easy to precipitate and scale during reaction distillation, clogging pipelines, resulting in scaling and difficulty in withdrawal. Using organic base sodium alcoholate as a catalyst can enhance the solubility of the catalyst in the reaction solution, and the esterification conversion rate of cyclic carbonates can also be significantly increased to more than 80%, but due to the strong interaction between sodium alcoholate and cyclic carbonates, symmetrical chain carbonates and diols, serious entrainment and product pollution occur during operation. Even though the sodium methoxide and alcoholamine compounds proposed in CN03135834 form a complex and have good solubility in the reaction solution and homogeneously synthesize chain carbonates, there are still problems such as difficulty in evaporating the product and high energy consumption for separating the catalyst and the product. Summary of the invention

[0004] The object of the present invention is to provide a method for synthesizing chain carbonate by catalyzing cyclic carbonate transesterification with low saturated vapor pressure in reaction liquid. The method comprises the following steps: preparing alkali metal ion liquid for catalyzing cyclic carbonate and alkyl alcohol transesterification to synthesize chain carbonate and diol, enhancing the compatibility of the reaction liquid including carbonate derivatives and alkali metal ion liquid catalyst, so as to reduce the ineffective use of catalyst and reduce separation energy consumption.

[0005] The present invention provides a method for synthesizing chain dialkyl carbonate by catalyzing cyclic carbonate transesterification, using alkali metal ionic liquid as a catalyst, and catalyzing cyclic carbonate to obtain chain carbonic acid diester and diol products through transesterification under normal pressure conditions, wherein the alkali metal ionic liquid cationic structural unit includes alkylamine cation, imidazolium cation, 1-methylimidazolium cation, 1-butyl-3-methylimidazolium cation, 1-butyl-2,3-dimethylimidazolium cation, pyridyl cation or pyrrolyl cation. The anionic unit is derived from an alkali metal halide, and its structure is [M x N y ] - , M represents any metal among Zn, Fe, and Al, N represents any halogen among Cl and Br, x=any one of 1, 2, and 3, and y=any one of 3, 4, 5, and 7.

[0006] The present invention provides a method for catalytic synthesis of chain carbonate, including the preparation of alkali metal ionic liquid, wherein the preparation process is that after the alkali metal salt is in contact with the Lewis alkaline ionic liquid, in a specific temperature, atmosphere environment, time and other factors, the metal-based Lewis alkaline ionic liquid is combined by covalent bonds and ionic bonds to generate a metal-based Lewis alkaline ionic liquid with an N-based structure as a cationic unit and a metal halide as an anionic structural unit, wherein the alkali metal salt involved includes any one of ZnCl2, ZnBr2, FeCl3 or AlCl3, and the Lewis alkalinity of the ionic liquid is provided by a cationic unit containing an N-based structure, including any one of an alkylamine cation, 1-methylimidazolium cation, 1-butyl-3-methylimidazolium cation, 1-butyl-2,3-dimethylimidazolium cation, pyridyl cation, and pyrrole cation. The specific temperature range is 60 to 120° C., the atmosphere environment is usually selected from an inert gas atmosphere including N2 or Ar gas environment, without solvent, and the time is generally 2 to 12 hours. The prepared alkali metal ionic liquid is dried in an inert environment and stored in an inert atmosphere. It is used to catalyze the transesterification of cyclic carbonates and alkyl alcohols to synthesize chain carbonates and diols, the reaction temperature is 50-120°C, the pressure is one of normal pressure or autogenous pressure, and the catalyst amount is 0.5-20wt%, wherein the cyclic carbonate includes any one of cyclic ethylene carbonate and cyclic propylene carbonate. The alkyl alcohol includes any one of methanol, ethanol, n-propanol, isopropanol or butanol. The chain carbonate diester refers to any one of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, diisopropyl carbonate and dibutyl carbonate. The diol refers to ethylene glycol. After the reaction is completed, the reaction solution and the ionic liquid are separated by extraction, and the extractant is usually selected from any one of ethyl acetate, toluene, dichloromethane, methyl formate, acetonitrile, ether and chloroform, and the collected reaction mixture is quantitatively analyzed by chromatography.

[0007] The method for synthesizing linear carbonate by transesterification of cyclic carbonate catalyzed by alkali metal ionic liquid provided by the present invention has the following effects and benefits:

[0008] Lewis alkaline ionic liquids have good compatibility with reaction raw materials, and cyclic carbonates and alkyl alcohols can easily contact catalytic active sites. The introduction of alkali metal-based anion structural units in the catalyst structure can greatly alleviate the solidification of alkali metal salts in the reaction system and avoid the phenomenon of pipeline blockage in the reaction distillation equipment during the scale-up research. The adjustable and designable anions and cations of alkali metal ionic liquids are conducive to improving the strength of their alkalinity by designing anion and cation structural units, and ultimately obtaining a highly selective catalytic reaction effect. The low saturated steam of ionic liquids is more conducive to solving the problem of product contamination caused by reaction raw materials and catalysts that are commonly generated during the scale-up process. The synthesis of chain carbonates including dimethyl carbonate, diethyl carbonate, and dipropyl carbonate by catalyzing cyclic carbonates with alkali metal-based ionic liquids can change the structure of the target chain carbonate product by changing different alkyl alcohol raw materials. The operation is simple, and the catalyst and product separation process is relatively easy, which is conducive to improving the purity of the product and has the potential to easily obtain high-quality electronic-grade chain carbonate products. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 [Bmim] provided by the specific embodiment 1 of the present invention + [ZnBr3] - The state of the structure changes with temperature. DETAILED DESCRIPTION

[0010] The method for synthesizing linear carbonate by ester exchange of cyclic carbonate catalyzed by alkali metal ionic liquid of the present invention has the following embodiments, which are convenient for understanding the content of the present invention, but do not represent or limit the scope of protection of the present invention without departing from the purpose of the present invention, and do not limit the content of the present invention in any way.

[0011] Example 1 Catalyst [Bmim] + [ZnBr3] - Synthesis

[0012] 0.01 mol of 1-butyl-3-methylimidazolium bromide and an equal molar amount of ZnBr2 were added to a three-necked round-bottom flask protected by a dry and inert high-purity N2 atmosphere, and mixed evenly with magnetic stirring at 80°C. After 30 minutes, the crystal water was removed and the reaction was continued for 4 hours to obtain Lewis alkali metal-based ionic liquid [Bmim] + [ZnBr3] - (See attached figure for the structure).

[0013] Example 2 Catalyst [Bmim] + [ZnBr2Cl] - Synthesis

[0014] 0.01 mol of 1-butyl-3-methylimidazolium bromide and an equal molar amount of ZnCl2 were added to a three-necked round-bottom flask protected by a dry and inert high-purity N2 atmosphere, and mixed evenly with magnetic stirring at 80°C. After 30 minutes, the crystal water was removed and the reaction was continued for 4 hours to obtain Lewis alkali metal-based ionic liquid [Bmim] + [ZnBr3] - .

[0015] Example 3 Catalyst [Bmim] + [ZnCl3] - Synthesis

[0016] 0.01 mol of 1-butyl-3-methylimidazolium chloride and an equal molar amount of ZnCl2 were added to a three-necked round-bottom flask protected by a dry and inert high-purity N2 atmosphere, and mixed evenly with magnetic stirring at 80°C. After 30 minutes, the crystal water was removed and the reaction was continued for 4 hours to obtain Lewis alkali metal-based ionic liquid [Bmim] + [ZnCl3] - .

[0017] Example 4 Catalyst [Bmim] + [Zn2Br5] - Synthesis

[0018] 0.01 mol 1-butyl-3-methylimidazolium bromide and 0.02 mol ZnBr2 were added to a three-necked round-bottom flask protected by a dry and inert high-purity N2 atmosphere, and mixed evenly by magnetic stirring at 80°C. After 30 minutes, the crystal water was removed and the reaction was continued for 4 hours to obtain Lewis alkali metal-based ionic liquid [Bmim] + [Zn2Br5] - .

[0019] Example 5 Catalyst [Bmim] + [Zn2Cl5] - Synthesis

[0020] 0.01 mol 1-butyl-3-methylimidazolium chloride and 0.02 mol ZnCl2 were added to a three-necked round-bottom flask protected by a dry and inert high-purity N2 atmosphere, and mixed evenly by magnetic stirring at 80°C. After 30 minutes, the crystal water was removed and the reaction was continued for 4 hours to obtain Lewis alkali metal-based ionic liquid [Bmim] + [Zn2Cl5] - .

[0021] Example 6 Catalyst [BDmim] + [Zn2Br5] - Synthesis

[0022] 0.01 mol 1-butyl-2,3-dimethylimidazolium bromide and 0.02 mol ZnBr2 were added to a three-necked round-bottom flask protected by a dry and inert high-purity N2 atmosphere, and mixed evenly by magnetic stirring at 80°C. After 30 minutes, the crystal water was removed and the reaction was continued for 4 hours to obtain Lewis alkali metal-based ionic liquid [BDmim] + [Zn2Br5] - .

[0023] Example 7 Catalyst [BDmim] + [Zn2Cl5] - Synthesis

[0024] 0.01 mol 1-butyl-2,3-dimethylimidazolium chloride and 0.02 mol ZnCl2 were added to a three-necked round-bottom flask protected by a dry and inert high-purity N2 atmosphere, and mixed evenly by magnetic stirring at 80°C. After 30 minutes, the crystal water was removed and the reaction was continued for 4 hours to obtain Lewis alkali metal-based ionic liquid [BDmim] + [Zn2Cl5] - .

[0025] Example 8 Transesterification

[0026] [Bmim] + [ZnCl3] - , methanol and cyclic ethylene carbonate were added in sequence into a 50 mL round-bottom flask with a reflux condenser, where [Bmim] + [ZnCl3] - The added amount is 20 mol% of the cyclic ethylene carbonate, the amount of methanol is 8 times the molar amount of cyclic ethylene carbonate (i.e., the alcohol-ester molar ratio is 8:1), the added amount of cyclic ethylene carbonate is 0.10 mol, the reaction temperature is set at 80°C, the magnetic stirring speed is 300 r / min, and the reaction is carried out for 6 hours. After the reaction is completed, the alkaline ionic liquid and the reaction mixture are separated by low-temperature centrifugation, and the received reaction mixture is used for chromatographic quantitative analysis, and it is determined that the conversion rate of cyclic ethylene carbonate is 65.1%, and the selectivity of dimethyl carbonate is 70.6%.

[0027] Example 9

[0028] [Bmim] + [Zn2Br5] - , methanol and cyclic ethylene carbonate were added in sequence into a 50 mL round-bottom flask with a reflux condenser, where [Bmim] + [Zn2Br5] -The added amount accounts for 20 mol% of the cyclic ethylene carbonate, the amount of methanol used accounts for 8 times the molar amount of cyclic ethylene carbonate (i.e., the alcohol-ester molar ratio is 8:1), the amount of cyclic ethylene carbonate added is 0.10 mol, the reaction temperature is set at 80°C, the magnetic stirring speed is 300 r / min, and the reaction is carried out for 6 hours. After the reaction is completed, the alkaline ionic liquid and the reaction mixture are separated by low-temperature centrifugation, and the received reaction mixture is used for chromatographic quantitative analysis, and it is determined that the conversion rate of cyclic ethylene carbonate is 15.3%, and the selectivity of dimethyl carbonate is 37.4%.

[0029] Example 10

[0030] [Bmim] + [Zn2Cl5] - , methanol and cyclic ethylene carbonate were added in sequence into a 50 mL round-bottom flask with a reflux condenser, where [Bmim] + [Zn2Cl5] - The added amount accounts for 20 mol% of the cyclic ethylene carbonate, the amount of methanol used accounts for 8 times the molar amount of cyclic ethylene carbonate (i.e., the alcohol-ester molar ratio is 8:1), the amount of cyclic ethylene carbonate added is 0.10 mol, the reaction temperature is set at 100°C, the magnetic stirring speed is 300 r / min, and the reaction is carried out for 4 hours. After the reaction is completed, the alkaline ionic liquid and the reaction mixture are separated by low-temperature centrifugation, and the received reaction mixture is used for chromatographic quantitative analysis, and it is determined that the conversion rate of cyclic ethylene carbonate is 71.7%, and the selectivity of dimethyl carbonate is 97.8%.

[0031] Embodiment 11

[0032] [BDmim] + [ZnBrCl2] - , methanol and cyclic ethylene carbonate were added in sequence into a 50 mL round-bottom flask with a reflux condenser, where [BDmim] + [ZnBrCl2] - The added amount accounts for 20 mol% of the cyclic ethylene carbonate, the amount of methanol used accounts for 10 times the molar amount of cyclic ethylene carbonate (that is, the alcohol-ester molar ratio is 10:1), the amount of cyclic ethylene carbonate added is 0.10 mol, the reaction temperature is set at 100°C, the magnetic stirring speed is 300 r / min, and the reaction is carried out for 4 hours. After the reaction is completed, the alkaline ionic liquid and the reaction mixture are separated by low-temperature centrifugation, and the received reaction mixture is used for chromatographic quantitative analysis, and it is determined that the conversion rate of cyclic ethylene carbonate is 52.2%, and the selectivity of dimethyl carbonate is 31.1%.

[0033] Example 12

[0034] [BDmim] + [Zn2Cl5] -, methanol and cyclic ethylene carbonate were added in sequence into a 50 mL round-bottom flask with a reflux condenser, where [BDmim] + [Zn2Br5] - The added amount accounts for 20 mol% of the cyclic ethylene carbonate, the amount of methanol used accounts for 8 times the molar amount of cyclic ethylene carbonate (i.e., the alcohol-ester molar ratio is 8:1), the amount of cyclic ethylene carbonate added is 0.10 mol, the reaction temperature is set at 100°C, the magnetic stirring speed is 300 r / min, and the reaction is carried out for 4 hours. After the reaction is completed, the alkaline ionic liquid and the reaction mixture are separated by low-temperature centrifugation, and the received reaction mixture is used for chromatographic quantitative analysis, and it is determined that the conversion rate of cyclic ethylene carbonate is 64.1%, and the selectivity of dimethyl carbonate is 99.8%.

[0035] Example 13

[0036] [BDmim] + [Zn2Cl5] - , ethanol and cyclic ethylene carbonate were added in sequence into a 50 mL round-bottom flask with a reflux condenser, wherein [BDmim] + [Zn2Cl5] - The added amount accounts for 20 mol% of the cyclic ethylene carbonate, the amount of ethanol accounts for 10 times the molar amount of cyclic ethylene carbonate (i.e., the alcohol-ester molar ratio is 10:1), the added amount of cyclic ethylene carbonate is 0.10 mol, the reaction temperature is set at 100°C, the magnetic stirring speed is 300 r / min, the reaction is carried out for 6 hours, and after the reaction is completed, the alkaline ionic liquid and the reaction mixture are separated by low-temperature centrifugation, and the received reaction mixture is used for chromatographic quantitative analysis, and it is determined that the conversion rate of cyclic ethylene carbonate is 76.3%, and the selectivity of diethyl carbonate is 65.7%.

[0037] Embodiment 14

[0038] [BDmim] + [Zn2Cl5] - , ethanol and cyclic propylene carbonate were added in sequence into a 50 mL round-bottom flask with a reflux condenser, where [BDmim] + [Zn2Cl5] - The added amount accounts for 20 mol% of the cyclic propylene carbonate, the amount of ethanol accounts for 10 times the molar amount of the cyclic propylene carbonate (i.e., the alcohol-ester molar ratio is 10:1), the amount of cyclic propylene carbonate added is 0.10 mol, the reaction temperature is set at 100°C, the magnetic stirring speed is 300 r / min, the reaction is carried out for 6 hours, and after the reaction is completed, the alkaline ionic liquid and the reaction mixture are separated by low-temperature centrifugation, and the received reaction mixture is used for chromatographic quantitative analysis, and it is determined that the conversion rate of cyclic propylene carbonate is 28.4%, and the selectivity of diethyl carbonate is 45.7%.

[0039] Although the above content has been described in detail with general descriptions and specific embodiments of the present invention, it is obvious to those skilled in the art that some modifications or improvements can be made to the present invention by ordinary persons in the art. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection claimed by the present invention.

Claims

1. A method for synthesizing a linear carbonic acid diester by ester exchange of a cyclic carbonate catalyzed by an alkali metal ionic liquid, characterized in that: The cationic structural unit of the alkali metal ion liquid comprises any one of alkylamine cations, 1-methylimidazolium cations, 1-butyl-3-methylimidazolium cations, 1-butyl-2,3-dimethylimidazolium cations and pyridyl cations, and is matched with anionic structural units formed from alkali metal halides. The alkalinity is improved by changing the anionic and cationic structural units, and the alkali metal ion liquid is used to catalyze the ester exchange of cyclic carbonates to synthesize chain carbonic acid diesters including dimethyl carbonate and diethyl carbonate. The alkali metal ion liquid is separated from the product by low-temperature centrifugation. The alkali metal halide is any one of ZnCl2, ZnBr2, FeCl3 and AlCl3; and the cyclic carbonate is any one of cyclic ethylene carbonate and cyclic propylene carbonate.

2. The method for preparing an alkali metal ionic liquid according to claim 1, characterized in that After the following steps: First, the alkali metal ionic liquid is prepared by an alkali metal halide salt and an N-heterocyclic halide salt providing a cationic structural unit containing a N heteroatom, and an alkali metal halide providing an alkali metal anion structural unit, and an ionization reaction occurs in a specific temperature range and gas atmosphere for a certain period of time to generate an alkali metal ionic liquid. The alkylamine halide salt is any one of tetrapropylammonium chloride, tetraethylammonium chloride and tetrabutylammonium chloride; the N-heterocyclic halide salt is any one of 1-methylimidazolium chloride, 1-methylimidazolium bromide, 1-butyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium bromide, 1-butyl-2,3-dimethylimidazolium chloride, 1-propylpyridinium chloride, hexadecylpyridinium chloride, 1-butyl-4-methylpyridinium chloride, and dodecylpyridinium chloride. Second, the specific temperature range refers to 60 to 120° C., the gas atmosphere refers to an inert atmosphere including N 2 or Ar environment, and the reaction time refers to a reaction time of 2 to 12 hours. Third, after the reaction is completed, the alkali metal ion liquid is obtained and sealed in an inert gas environment for storage for later use.

3. The method according to claim 1 wherein the catalyst is used to synthesize a linear carbonic acid diester, characterized in that The method for synthesizing carbonic acid diester comprises the following steps: First, a certain amount of alkali metal ion liquid, cyclic carbonate and alkyl alcohol are uniformly mixed and heated to a reaction temperature to synthesize a chain carbonate product and a corresponding diol. Second, a certain amount of alkali metal ionic liquid refers to 0.5 to 20 wt% of the weight of the cyclic carbonate, the cyclic carbonate refers to any one of cyclic ethylene carbonate and cyclic propylene carbonate, the chain carbonate refers to any one of dimethyl carbonate, diethyl carbonate, diisopropyl carbonate, dipropyl carbonate and dibutyl carbonate, and the diol refers to ethylene glycol. Third, the reaction temperature refers to 50 to 120° C., and the reaction mixture completes the reaction under any one of normal pressure and autogenous pressure. After the reaction is completed, the reaction liquid and the alkali metal ion liquid are separated by extraction to collect the reaction product. The extractant is selected from any one of ethyl acetate, toluene, dichloromethane, methyl formate, and acetonitrile. The catalyst can be reused, and the product is quantitatively analyzed by chromatography.

4. The method for synthesizing chain carbonic acid diester according to claim 3, wherein The added alkyl alcohol is calculated based on the molar amount of the cyclic carbonate, and the molar amount of the alkyl alcohol is 1 to 12 equivalents of the cyclic carbonate. The alkyl alcohol refers to one of methanol, ethanol, n-propanol, isopropanol and n-butanol.

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